Photographic material comprising an antistatic coating

ABSTRACT

This application describes photographic material which comprises a support base having coated thereon on one or both sides at least one photographic emulsion layer, and having coated on each topmost emulsion layer a gelatin supercoat layer, there being present on at least one supercoat layer an antistatic layer which is a layer of a homopolymer of a compound of general formula I: (CH2 CH - CH2)2NR1R2 X I where R1 and R2 are each hydrogen atoms or alkyl groups and X is an anion, or a copolymer thereof with minor amounts of other ethylenically unsaturated monomers, the said homo- or copolymer layer having been coated from a lower primary alcohol solution, or photographic material which comprises a support base which has on one side thereof at least one photographic emulsion layer and which has on the other side an antistatic layer which is a layer of a homopolymer of a compound of the above formula I or a copolymer thereof with minor amounts of other ethylenically unsaturated monomers.

United States Patent [72] Inventor Henry Walter Wood llford, England[21] Appl. No. 838,350 [22] Filed July 1, 1969 [45] Patented Sept. 21,1971 [73] Assignee Ilford Limited llford, England [32] Priority July 3,1968 [33] Great Britain l 31,705/68 [54] PHOTOGRAPHIC MATERIALCOMPRISING AN ANTISTATIC COATING 8 Claims, No Drawings [52] [1.8. Ci96/87 A [51] lnt. Cl G03c 1/82 [50] Field of Search 96/87 A,

[56] References ited UNITED STATES PATENTS 3,399,995 9/1968 Winchell96/87 Primary Examiner-Ronald H. Smith AttorneyCushman, Darby & CushmanABSTRACT: This application describes photographic material whichcomprises a support base having coated thereon on one or both sides atleast one photographic emulsion layer, and having coated on each topmostemulsion layer a gelatin supercoat layer, there being present. on atleast one supercoat layer an antistatic layer which is a layer of ahomopolymer ofa compound of general formula I:

where R and R are each hydrogen atoms or alkyl groups and X.is an anion,or a copolymer thereof with minor amounts of other ethylenicallyunsaturated monomers, the said homoor copolymer layer having been coatedfrom a lower primary alcohol solution, or photographic material whichcomprises a support base which has on one side thereof at least onephotographic emulsion layer and which has on the other side anantistatic layer which is a layer of a homopolymer of a compound of theabove formula I or a copolymer thereof with minor amounts of otherethylenically unsaturated monomers.

PHOTOGRAPHIC MATERIAL COMPRISING AN ANTllSTATIC COATING This inventionrelates to photographic film material provided with an antistatic layerand to the production of such film material.

It is known that photographic film material exhibits a tendency to pickup electrostatic charges during the course of its manufacture and alsowhen it is being processed. When an electrostatically charged film isdischarged so called static marks are produced. These marks show asareas of local overexposure on the developed film. It is possible toreduce the tendency of photographic film to pick up electrostaticcharges by the provision of a layer which has a relatively highelectroconductivity. Any electrostatic charge picked up by a film havingsuch a layer rapidly leaks to earth without causing a discharge.

It is the object of the present invention to provide photographicmaterial which comprises such a layer of relatively high conductivity.

According to the present invention, therefore, there is providedphotographic material which comprises a support base having coatedthereon on one or both sides at least one photo graphic emulsion layer,and having coated on each topmost emulsion layer a gelatin supercoatlayer, there being present on at least one supercoat layer a layer of ahomopolymer of a compound of general formula I:

where R and R are each hydrogen atoms or alkyl groups and X is an anion,or a copolymer thereof with minor amounts of other ethylenicallyunsaturated monomers, the said homeor copolymer layer having been coatedfrom a lower primary alcohol solution, or photographic material whichcomprises a support base which has on one side thereof at least onephotographic emulsion layer and which has on the other side a layer of ahomopolymer of a compound of the above formula I or a copolymer thereofwith minor amounts of other ethylenically unsaturated monomers.

By minor amounts of other ethylenically unsaturated monomers is meant atmost 7 percent of other monomers.

By lower primary alcohol is meant a primary alcohol which comprises upto six carbon atoms, e.g. methanol, ethanol, butanol and methylcellosolve. The preferred primary alcohol is methanol.

There was described in our copending application Ser. No. 832,021 filedJune It), 1969, photographic emulsions which comprise homopolymers ofcompounds of formula I and copolymers thereof. The effect of addingthese compounds to photographic emulsions was shown to be an increase inphotographic speed of the emulsion. Thus when homopolymers of compoundsof the above formula I and copolymers thereof are included inphotographic material as a conductive layer it is important that they donot diffuse into the photographic emulsion layer.

It was found that when there was a gelatin supercoat over the emulsionlayer or layers and the polymeric compounds were coated from a primaryalcohol solution, that the alcohol did not swell the gelatin supercoatlayer but evaporated rapidly leaving a layer of the polymeric substancewhich did not diffuse into the underlying emulsion layer. Whenhomopolymers of compounds of formula I or copolymers thereof were coatedonto the supercoat layer in aqueous solution, because the water swelledthe supercoat layer, a proportion of the polymeric substance diffusedinto the photographic emulsion layer end affected its photographicproperties.

However when the homopolymers of formula I or copolymers thereof arecoated onto the back of the photographic material, i.e., the side ofphotographic material which has no emulsion coated thereon, they may becoated from aqueous solution or from a lower primary alcohol solution.In this case the impermeable base protects the photographic emulsionfrom the coating solution.

The invention is of particular use in regard to X-ray films which arecoated on each side with a photographic emulsion layer and with asupercoat layer. In the case of such film material it is preferred thateach supercoat layer has coated thereon a layer ofa homopolymer ofacompound of formula I or a copolymer thereof, the said layer having beencoated from a lower primary alcohol solution.

It is to be understood, however that the invention also coversphotographic material which comprises a base support having on one sideat least one photographic emulsion layer, and having coated on the topmost emulsion layer a gelatin supercoat layer, there being present onthe supercoat layer a layer of a homopolymer of a compound of formula Ior a copolymer thereof, this said layer having been coated from a lowerprimary alcohol solution and on the other side a layer of a homopolymerof a compound of formula I or a copolymer thereof.

It is thought that the homopolymers of use in the present invention havethe general formula II:

where R,, R and X have the meanings assigned to them above and n is anintegral number.

Homopolymers of the above type have been described by Butler and Angelo.J. Amer. Chem. Soc. 1957, 79, 3,128.

Copolymers which comprise units of the above formula II have beendescribed by Schuller et al. Journal of Chemical Engineering Date. 1959,4, 1,273. The copolymers may be of different types, for example thecopolymer may be a copolymer which comprises a chain of units of generalformula II, there being dispersed in the chain units derived from otherethylenically unsaturated monomers such as vinyl pyrrolidone.Alternatively the copolymer may be a cross-linked copolymer whichcomprises cross-linked chains of units of general formula II there beingdispersed in the chain units derived from compounds of general formula Ibut wherein at least one of R or R is an allyl group. The presence ofthese allyl groups causes cross-linking between the chains. In anothertype of copolymer the homopolymer chains or the copolymer chains, i.e.,chains which comprise dispersed therein units derived from othermonomers such as vinyl pyrrolidone, may be cross-linked by compoundshaving two double bonds such as methylenebisacrylamide.

The effect of cross-linking the homopolymer or the random copolymer isto increase the effective molecular weight of the polymeric material andto decrease its solubility in alcohol. Thus only a small amount ofcross-linking can take place before the homopolymer or copolymer becomesinsoluble. On the other hand in some instances it is desirable that somecross-linking has taken place since this renders the polymeric materialless likely to diffuse.

In the preferred compounds of formula I for use in the invention R and Rare each alkyl groups and most preferably are ethyl or methyl groups.

The following examples will serve to illustrate the invention.

EXAMPLE I Pieces of an X-ray film bearing on each side of the support,in order, a photographic silver halide emulsion layer and a gelatinsupercoat layer were further coated in the dry state (on both sides)with methanolic solutions of polymers A and B respectively.

Polymer A: a copolymer of the compound of general formula I as givenabove wherein R =R ethyl and X bromide, with 1 percent acrylamide.

Polymer B: a copolymer of the compound of general formula I as givenabove wherein R,=R methyl and X chloride,

The results of the two tests are shown in table I below.

TABLE I Polymer Methanol Test l Test 2 soln. log R v./cm.

It can be seen that the polymers have given an improved result, asjudged by either test. Polymer B is more active than A and this is ageneral feature of compounds having methyl groups on the nitrogen atoms.

Coating from a I percent methanolic solution of polymer gave a coatingweight of approximately 5 mg./dm. and other strengths pro rata.

EXAMPLE II.

Pieces of .an X-ray film bearing on each side of the support, in order,a photographic silver halide emulsion layer and a gelatin supercoatlayer were further coated in the dry state on each side with amethanolic solution of the following polymers:

A: a copolymer of the compound of general formula I wherein R,=R, ethyland X bromide, with 1 percent acrylamide (polymer A of Example I).

C: a copolymer of the compound of general formula I wherein R,=R methyland X chloride, with 1 percent acrylamide.

D: a copolymer of the compound of general formula I wherein R, and R aremethyl and X is chlorine with 5 percent vinylpyrrolidone.

The following two tests were applied to the dried pieces of X-ray filmat percent R.H.

l. The resistivity of the assembly was measured under an appliedpotential of IOkV; the result being expressed as log R q).

2. The pieces of film were passed through a pair of rubber rollers tocreate a charge which was measured by an adjacent field meter; theresult being expressed as V./cm. The peak field strength is shown intable 2 which follows together with the value after a decay time of 20seconds.

It can be seen that the performance of the polymers is main tained atthe lower humidity prevailing in the example. Again the compounds withmethyl roups on the nitrogen are more effective. After a short time $20inches), no static can be detected on the films with coatings ofpolymers C and D.

The adjacent field meter used in the above experiment is described inour Belgian Pat. No. 726,369.

I claim as my invention:

1. Photographic material which comprises a film support having coatedthereon on one or both sides at least one photographic emulsion layer,and having coated on each top-most emulsion layer a gelatin supercoatlayer, there being present on at least one supercoat layer as anantistatic layer a layer of a homopolymer of a compound of the generalformula:

where R, and R are each hydrogen atoms or alkyl groups and X is ananion, or a copolymer thereof with up to 7 percent of otherethylenically unsaturated monomers, the said homoor copolymer layerhaving been coated from a lower primary alcohol solution.

2. Photographic material according to claim 1 wherein in the compoundtherein defined R, and R are each methyl groups.

3. Photographic material according to claim I wherein the copolymerlayer is a copolymer of the compound defined in claim 1 together with upto 7 percent of vinylpyrrolidone. acrylamide or styrene.

4. Photographic material which comprises a film support which has on oneside thereof at least one photographic emulsion layer and which has onthe other side an antistatic layer which is a layer of a homopolymer ofa compound of the general formula where R, and R are each hydrogen atomsor alkyl groups and X is an anion, or a copolymer thereof with up to 7percent of other ethylenically unsaturated monomers.

5. Photographic material according to claim 4 wherein in the compoundtherein defined R, and R are each methyl groups.

6. Photographic material according to claim 4 wherein the copolymerlayer is a copolymer of the compound defined in claim 4 together with upto 7 percent of vinylpyrrolidone, acrylamide or styrene.

7. X-ray film material which comprises a film support having coated oneach side a photographic emulsion layer and having coated on eachemulsion layer a gelatin supercoat layer, there being present on eachsupercoat layer an antistatic layer which is a layer ofa homopolymer ofa compound of the general formula:

where R, and R are each hydrogen atoms or alkyl groups and X is ananion, or a copolymer thereof with up to of other ethylenicallyunsaturated monomers, the said homoor copolymer layer having been coatedfrom a lower primary alcohol solution.

8. A process for the preparation of an antistatic layer on photographicmaterial which comprises a film support having coated thereon on one orboth sides at least one photographic emulsion layer, and having coatedon each top-most emulsion layer a supercoat layer, which processcomprises coating on at least one supercoat layer a lower primaryalcohol solution of a homopolymer of a compound of the general formula:

where R, and R are each hydrogen atoms or alkyl groups and X is ananion, or a copolymer thereof with up to 7 percent of otherethylenically unsaturated monomers and removing the lower primaryalcohol.

2. Photographic material according to claim 1 wherein in the compoundtherein defined R1 and R2 are each methyl groups.
 3. Photographicmaterial according to claim 1 wherein the copolymer layer is a copolymerof the compound defined in claim 1 together with up to 7 percent ofvinylpyrrolidone, acrylamide or styrene.
 4. Photographic material whichcomprises a film support which has on one side thereof at least onephotographic emulsion layer and which has on the other side anantistatic layer which is a layer of a homopolymer of a compound of thegeneral formula (CH2 CH-CH2)2NR1R2 X where R1 and R2 are each hydrogenatoms or alkyl groups and X is an anion, or a copolymer thereof with upto 7 percent of other ethylenically unsaturated monomers. 5.Photographic material according to claim 4 wherein in the compoundtherein defined R1 and R2 are each methyl groups.
 6. Photographicmaterial according to claim 4 wherein the copolymer layer is a copolymerof the compound defined in claim 4 together with up to 7 percent ofvinylpyrrolidone, acrylamide or styrene.
 7. X-ray film material whichcomprises a film support having coated on each side a photographicemulsion layer and having coated on each emulsion layer a gelatinsupercoat layer, there being present on each supercoat layer anantistatic layer which is a layer of a homopolymer of a compound of thegeneral formula: (CH2 CH-CH2)2NR1R2 X where R1 and R2 are each hydrogenatoms or alkyl groups and X is an anion, or a copolymer thereof with upto of other ethylenically unsaturated monomers, the said homo- orcopolymer layer having been coated from a lower primary alcoholsolution.
 8. A process for the preparation of an antistatic layer onphotographic material which comprises a film support having coatedthereon on one or both sides at least one photographic emulsion layer,and having coated on each top-most emulsion layer a supercoat layer,which process comprises coating on at least one supercoat layer a lowerprimary alcohol solution of a homopolymer of a compound of the generalformula: (CH2 CH-CH2)2NR1R2 X where R1 and R2 are each hydrogen atoms oralkyl groups and X is an anion, or a copolymer thereof with up to 7percent of other ethylenically unsaturated monomers and removing thelower primary alcohol.